Caption: View of LEP, the Large Electron-Positron collider at CERN, the European centre for particle physics near Geneva. LEP accelerates electrons & positrons to an energy of 50 GeV. It is housed in a circular tunnel 100m underground & 27km in circumference. The particles travel in opposite directions inside a narrow aluminium pipe which passes through the large electromagnets seen in this picture. The brown & white magnets are dipoles that bend the particles around the ring; the blue magnets are quadrupoles that focus them in tight bunches. The particles collide at 4 points around the tunnel where their interactions are observed by 4 giant detectors. LEP starts operations in July 1989. Photo taken April 1989.